1. Field of the Invention
The present invention relates, generally, to methods and apparatus for increasing the useful life of temperature-sensitive automotive components by limiting the magnitude and duration of temperature extrema in the immediate component environment, and more particularly to a system for directing an air stream over the components during vehicle operation and for a predetermined period thereafter.
2. Related Application
This application is an improvement upon an earlier filed U.S. application Ser. No. 07/311,149 filed on Feb. 14, 1989, now U.S. Pat. No. 4,976,327, and entitled "A Battery Module for the Engine Compartment of an Automobile", commonly assigned herewith. The entire disclosure of Ser. No. 07/311,149 is hereby incorporated by reference.
3. Description of the Prior Art
The prevalence of electronic and other temperature-sensitive components in newer model vehicles continues to increase. The demand for on-board computers, electronic ignitions, antilock brake system modules, and electronic engine controls, for example, has changed the face of automotive design in recent years. At the same time, the desire to maximize operator and passenger comfort results in these components being placed under the hood (the "underhood" area as used herein), under the car, and in the trunk. The introduction of comprehensive warranties of longer duration dictates that these components be able to withstand the harsh temperature fluctuations associated with these environments.
During stop-and-go city driving or while the engine is idling with no wind, the underhood air temperature remains well above ambient, often exceeding 200 degrees F in the southwest summer and 100 degrees F in the northern winter. When the air speed, from the fore to the aft direction with respect to the car, exceeds 5 mph, the underhood air temperature follows the ambient air temperature fairly closely. Virtually any breeze, if directed toward the front of the car, forces the underhood air temperature toward ambient; a steady wind over 5 mph maintains the underhood air temperature near the ambient air temperature.
At high temperatures such as those encountered in a vehicle trunk or under the hood, the performance of various temperature-sensitive components is impaired. Many electrical and electronic devices, for example, may be irreparably damaged at very high temperatures. In addition, battery water loss due to evaporation and, in some instances, boiling of the water caused by excessive charge rate results in the battery grids being subjected to accelerated corrosion. Moreover, the material comprising the battery plates tends to crumble after extended exposure to elevated temperatures. At extremely low battery temperatures, on the other hand, the performance of various components, including the battery, may also be impaired. Thus, it is desirable to minimize the duration and extent of both high and low temperature extremes.
Although temperature-sensitive components, and particularly the battery, receive some radiant heat from the engine, most of the increase in component temperature is caused by the temperature of the underhood air around the component, i.e., convective heat. The effects of radiative heat can be limited by at least two factors: physical barriers placed between the engine and the battery; and, during winter driving, the cold underhood air may cool the engine surface and inhibit the release of radiative heat to the battery. Convective and conductive heat, on the other hand, are not as easily compensated for. Presently known techniques employ passive air flow, i.e., air flow attributable to either wind or vehicle movement. This passive ram air is ducted from the outside of the car and directed at the component sought to be cooled. However, passive ram air is not exploitable when the engine is off absent a properly oriented wind.